1. Field of Invention
The present invention refers to an apparatus in electronic ignition systems.
2. Prior Art
In conjunction with outboard motors for boats, for example, very high demands are made today for reliable engine function even at very low revolution rates. Electronic ignition systems, which have been found to be very advantageous in such engines because they enable moisture-proof enclosure, are usually equipped with a charging coil for charging a capacitor in the electronic ignition system. The charging coil gets its induction from permanent magnets mounted on the engine flywheel. It has been found, however, that at low revolution rates and even in conjunction with starting, the generated charging voltages have not been sufficient to provide the necessary spark in the associated spark plug. One means for overcoming this disadvantage is to arrange several, e.g. three, core legs with charging coils for coaction with the pertinent charging circuit, said coils each contributing to building up the necessary charge in the capacitor. In this way there is obtained very reliable idling revolution rates for the engine as well as good starting characteristics. However, with increasing r.p.m. there are direct problems with over-voltages in the charging circuit, and accompanying risks of destroying participating components such as rectifiers, thyristors and the like.
In a modern outboard motor, the ignition apparatus is generally built together with a generator part to provide lighting energy and possibly charging energy for a battery. In connection therewith there is a demand for a plurality of magnet poles along the circumference of the flywheel for coacting with a plurality of core legs carrying generator coils. This arrangement brings with it complications with regard to the triggering operation per se, since the triggering coil will be affected by a plurality of magnetic fields passing it. It is thus possible to get triggering at undesired places along a flywheel revolution. It is further a requirement that the trigger voltage be kept within reasonable values and at constant levels for large ranges of revolution rates. Swedish Pat. No. 7401667-6 is typical.